1. Field of the Invention
This invention relates to a method of non-destructively measuring the pressure of a gas in a closed vessel, and, in particular, to a method of non-destructively measuring the pressure of gases in glass envelopes, such as autolamps and flashbulbs. Accordingly, it is a general object of this invention to provide new and improved methods of such character.
2. Description of the Prior Art
Various prior art methods of measuring pressure of a system assume that when a gas is introduced at a particular pressure into a system, and the system is sealed-off, the gas pressure is the same as the seal-off pressure and remains constant. Disadvantageously, no provision is made for leaks either during the time of pressurization or thereafter.
In the production of high intensity halogen headlights, there is a need to constantly monitor the gas fill pressure of the lamps. Usually, such measurement is manually performed, and, therefore, is slow and expensive. Thus, it is desired to provide a rapid and, preferably, non-destructive measurement of the gas pressure. One proposed approach of monitoring the pressure is by relating the intensity of the HBr band at 3.9-4.1 .mu.m to the increase in pressure. However, the glass used as the lamp envelope absorbs substantially in this region, thus lowering the sensitivity of the method. In addition, the content or HBr is generally only 0.2-0.3% by weight of the total gas content, leading to further error in measurement, assuming there is a signal at all. Furthermore, pressure increase causes broadening of the HBr band causing a further decrease in signal.